Description

Script `zkServer.sh` stops zookeeper by sending the java process a `kill -9` (SIGKILL). As there seems to be no technical reasons to use such a radical signal rather than the default SIGTERM (-15), I would propose to just use `kill` rather than `kill -9`.

My use case is for Systemd service files for Zookeeper which always consider Zookeeper java process as failing when a clean `stop` is issued.

There is no way to make this `status=9/KILL` to be recognized by
Systemd as a regular exit code, even with `SuccessExitStatus=9 KILL
SIGKILL`. On the other hand, turning this `kill -9` into a regular
`kill` (-15 implied) makes it: